Planting date and cultivar selection to manage southern blight in potatoes in the mid-Atlantic United States

Abstract

Incidence of southern blight caused by Sclerotium rolfsii Sacc. in potato (Solanum tuberosum L.) has increased across the mid-Atlantic region. To date, no potato cultivar is resistant to southern blight, and effective management with fumigants and fungicides has been inconsistent and uneconomical. This study evaluated impacts of four planting dates, ten commercial cultivars, and integrated effects of planting date and cultivar on southern blight incidence, yield, and tuber quality. Disease incidence varied by year, with fewer occurrences in 2019 (25%) than in 2018 (79%) or 2017 (64%), likely due to dry and warm weather. Despite the planting date by cultivar interaction, later plantings had greater disease incidence (85–94%) and lower tuber yield (1.8–9.4 Mg ha-1) and quality (47–78% marketable tubers) than earlier plantings. Planting date effects were likely driven by humid, warm weather later in the season that was conducive to disease and detrimental to crop development. Though cultivar responses varied across planting date-years, ‘Accumulator’ had the lowest disease incidences (36%) and greatest tuber yield (20.2 Mg ha-1) among tested cultivars. Conversely, ‘Adirondack Blue’ and ‘Dark Red Norland’ had the overall greatest incidence of S. rolfsii (33–100%) while ‘Yukon Gold’ had the lowest yield (0.3–24.1 Mg ha-1). Potato chipping cultivars tended to be less impacted by S. rolfsii than fresh market cultivars; however, additional studies are needed to elucidate potential mechanisms of disease resistance. This study indicates early planting dates and cultivar selection are an effective management approach to reduce S. rolfsii incidence on potato and maximize tuber yield.